Untitled

// Controller object Create Event:
SelectedObject = false;

// Object you want to click's Step Event:
if
SelectedObject = false and
point_in_rectangle(mouse_x,mouse_y,bbox_left,bbox_top,bbox_right,bbox_bottom)
    {
    if mouse_check_button_pressed(mb_left)
        {
        if SelectedObject = false
            {SelectedObject = id;}
        }
    } else
        {
        if SelectedObject = id
            {SelectedObject = false;}
        }

/*
if you have to check for collision with the object you have to change the
"point_in_rectangle(mouse_x,mouse_y,bbox_left,bbox_top,bbox_right,bbox_bottom)" with something like this:

collision_point(mouse_x,mouse_y,object_index,true,false)

*/